This invention relates to a device for displacement of at least two objects for the comparison of dimensions of these objects by means of a measuring apparatus and to a method for the comparison of dimensions by means of the aforementioned device.
The invention concerns particularly, but not exclusively, the field of dimensional control of gauge blocks, it being a matter of new blocks or of blocks which have already been used.
The device pertains preferably to the conventional comparison of a reference block and a block to be measured of the same length, but also the comparison of a single reference block and blocks to be measured of different lengths.
A gauge block is an object which has at least two parallel faces spaced apart by a very precise distance, referred to as length.
Gauge blocks are objects of very high precision which are currently used, for example, in workshops for mechanical manufacture, in particular for measuring lengths.
In terms of the ISO 3650 standard, a gauge block is a materialized measuring unit, usually of rectangular section, made of a material resistant to wear and tear, having two flat measurement faces parallel to each other, which must be able to adhere to measurement faces of other gauge blocks for making up assemblies, or to flat surfaces of the same finish of auxiliary surface planes used for length measurements.
Likewise in the terms of the ISO 3650 norm, the length of a gauge block, by convention, is the distance between each particular point of a measuring face and the flat surface of an auxiliary plane of the same material and of the same state of surface on which the other measuring face is attached.
Such gauge blocks are frequently manipulated and placed in contact with one another and/or in contact with other objects.
These mechanical contacts cause a progressive wear and tear of the faces of the blocks that determine their length.
Such wear and tear, however minute it is, changes therefore the length of the blocks, and leads to errors in measurement.
It is thus imperative that the blocks be periodically checked so that those which show abnormal wear and tear can be pinpointed in view of removing them from use.
For this check, it is known to compare, on the one hand, the spacing of the opposite faces which determine the length of each block used with, on the other hand, the spacing of opposite faces of a reference block.
Conventionally, the measurement of the length of a block is carried out between points of a plurality of pairs of points, for example, for a right-angled parallelepiped-shaped block, between points situated at the vertices of diagonals of opposite faces and between points situated at the intersection of diagonals of these faces.
To this end, a device is put in operation comprising:
a support, referred to as a measuring table, which defines a common supporting and sliding plane for the reference block and the block to be measured, and this for one of their faces concerned by the measurement,
a piece, referred to as a template, which is, on the one hand, situated above for maintaining the blocks in a predetermined position and orientation, by cooperating with the lateral faces of the blocks, and this while preserving their free support on the measuring table, and, on the other hand, is borne by a means of guiding along two intersecting axes parallel to the support plane in such a way as to allow a simultaneous displacement of the blocks.
The device preferably includes a means of assistance in guiding the displacement of the template along a preferred course for causing a simultaneous displacement of the two blocks in a way as to allow
the positioning of the reference block between two sensing elements of the measuring apparatus so as to allow a reading on this block by contact of the said sensing elements each on one of the opposite faces of the block,
the displacement of the reference block and that of the block to be checked in such a way as to substitute them, the one for the other, and to present the block to be checked between the said sensing elements, and this successively in each of the reading positions.
A measuring apparatus equipped with such a displacement device is extremely reliable, and its use is also easy and quick.
This state-of-the-art device gives good results, but it is faulted for causing a certain wear and tear on each reference block because the latter remains in contact on the measuring table during the readings carried out on the block to be checked.
A result which the invention aims to obtain is specifically a device for displacement of blocks which, while having all the advantages of the known device, noticeably reduces the wear and tear on the reference block.
To this end, the invention has as its subject matter a displacement device characterized in particular in that the template is made up of at least two separate parts which can be displaced separately from one another, of which:
a first part that comprises the stops intended for lateral maintenance of the reference block on the measuring table, and
at least one further part, referred to as the second part, that comprises the stops intended for lateral maintenance of at least one block to be checked.
The invention likewise has as its subject matter a method for comparison of dimensions by means of the aforementioned displacement device.